@BenediktBauer: The topics of the two sites overlap. I've participated a little in fitness.SE and got a very negative impression; there's a huge volume of people expressing their opinions, for which they don't have any evidence.
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Ben CrowellMar 13 '14 at 15:54

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@BenCrowell there's a word for that and it's "bro science". too bad that there's so much of this at fitness.SE.
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henningJul 4 at 19:54

1 Answer
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Some factors that you can't easily control play a clear role. These include genetics, being overweight,[Theisen] or having a previous injury. For example, people who want to lose weight may run in order to burn calories; they can't necessarily lose the weight before they start running so as to reduce their chance of getting hurt.

Changes in what you do

There is a large amount of consistent evidence that people get injured more frequently when they make a change in their activity. This could mean changing from stretching to not stretching, changing from not stretching to stretching, wearing different shoes, or running at a different pace or for a different distance.[Pereles,Reynolds]

Stretching and warming up

In general, scientific evidence doesn't support the common belief that stretching before playing sports prevents injuries.[McHugh] Of course this depends somewhat on the sport. In the case of running, a pre-run stretch has been found in a randomized trial to have no statistically significant effect on the incidence of injuries.[Pereles]

Cushioning of shoes

A number of studies have attempted to test whether shoes with more cushioning prevent injury. The results have not always been consistent, but in general there is no clear evidence that cushioning prevents injury.[Theisen] Barefoot runners and runners who use minimalist shoes do not have higher rates of injury, but switching from one type of shoe to another may cause problems; as with any change in what you do, it increases your risk of injury.

Running shoe companies have been telling runners for a long time that they need different shoes depending on whether their feet are normal, pronated, or supinated. This is not true.[Nielsen2]

Repetitive stress injuries

Most running injuries are repetitive stress injuries, or RSI's. As you run, you may be doing tiny amounts of invisible damage to various parts of your body. Normally this damage just heals up and you never even feel it. But if the long-term rate at which you do the damage to a certain body part outpaces the rate at which your body can heal it, your condition will gradually get worse.

As suggested by the term, RSI's are thought to be caused by a stress or load, such as tension or compression, placed on your musculoskeletal system. Most materials behave elastically when subjected to a certain amount of stress, so that when the stress is released, then go back to their original shape. Think of a rubber band being placed under tension, which is then released. But there is a limit on the amount of stress, called the elastic limit. Beyond this limit, the rubber band may be damaged.

When it comes to RSI's caused by running, there has been a lot of speculation that the really damaging stresses are the ones from impacts, such as the heel strike seen in the style of running used by most people who grow up in the industrialized world wearing shoes. The evidence seems to show that what's correlated the most with injuries is not the amount of force (load) experienced by your body parts but the rate of change of the force, which is called the load rate or impact loading.[Zadpoor][Davis] For example, if three people are piled on top of you, lying quietly, then your body is feeling a force equal to four times the usual force of gravity, but the force is not changing, so the load rate is zero. Measurements seem to show that when people wear running shoes, the load rate from their heel strikes is higher than the load rate experienced by barefoot runners.[Lieberman]

Unlike load rate, load itself doesn't seem to be correlated with injury.[Davis] In fact, impact is good for you. Your body seems to need some good hard impacts (about 4 gees or more) in order to have healthy bone density.[Tobias] This is an example of what's known as the "training effect," which is that when you do an activity that results in a certain optimal load, your body gets stronger. However, there is a higher level of load, called the "abusive load," that causes injury.

So the evidence seems to be that you should subject your body to impacts that are of just the right strength, and that they should be applied with a low load rate.

Volume and pace

This makes it pretty complicated to interpret medical studies of running injuries, because usually there is no detailed information about the load and load rate. One hypothesis[Nielsen] is that there are four different variables that should be studied:

volume -- how many miles you run per week

pace -- how fast you run

rapid change in volume

rapid change in pace

There is not much evidence that volume causes injury. For example, one study found that ultramarathoners who ran 200 miles experienced less harm to their bodies than those who ran "only" 100 miles.[Saugy] The interpretation is that at longer distances, runners reduce their pace, reducing the damage to their bodies.

Pace affects load, but it affects load rate even more. Load is proportional to the square of speed, but load rate goes like speed to the third power. For example, if you double your pace, the load rate is eight times higher.

In general, injuries are more likely when you change what you do, and that's the reason for hypothesizing that rapid changes in volume or pace are important variables. However, a study seems to show that the traditional 10% rule, i.e., not to change your volume by more than 10% per week, does not actually reduce injury.[Buist]

Conclusions

In summary, there is not much helpful evidence-based medicine on running injuries. Very little of the conventional wisdom among runners holds up scientifically, so at least you can stop putting time, energy, and money into following their advice. As far as I can tell, the only generic advice that seems to be supported by the evidence is:

Don't make sudden changes in what you do. Give your body time to adapt to changes.

Try to set your running pace so that it's fast enough to produce good health effects -- but it's possible that trying to run too fast may be harmful, especially if you try to ramp it up too quickly.

Nice answer. I didn't now that the 10% rule doesn't hold up. One more idea: Most factors that you discuss are about (training) stress; but so far you miss the other side of the coin: recovery and prevention. For example, sleep deprivation raises the level of cortisol, a hormone associated with over-training.
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henningJul 4 at 20:10

Fantastic answer! Just want to add, running is complex. If you haven't done regular running as a child, chances are your going to do a lot of mechanical in-efficient movements. Even so, just 1-2 hours with a track and field coach can help a lot with better movements.
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SoccermanJul 6 at 11:24